CHOOSING THE RIGHT DRIVING LINE: ARE YOU DRIVING THE RIGHT LINE?
How to Find the Right Driving Line
Probably the most fundamental aspect of driving a car on the track is to make sure that you are driving the “line”. The better you are at driving the line the faster you will go, right? It sounds simple enough but how come this is something that seems to always need adjusting/fine tuning? It is because there isn’t one “line” for every car and driver combination. In fact, the “line” can even change during an event or even a race based on the car’s handling changing or the grip levels changing. I think there is almost always a general path that all the cars should take but not all cars handle the same and it might be advantageous for one driver to take a slightly different approach to the same corner. So, how do you know if you are driving the right line for you and your car?
There are some rules that will get you heading in the right direction (pun intended!) and they are as follows:
- Open the radius or another way to put it is use all of the track. This is because steering slows the car down – the more you turn the car the slower you will go and if you can make the radius of a corner bigger then the faster you will go.
- You are apexing the corner too early if you run out of track exiting the corner.
- You are apexing the corner too late if you still have track available to use exiting the corner.
This is all great information but there are all sorts of things that can cause exceptions to these rules – such as maybe the very edge of the track where you are braking is more slippery when you are less than a foot off of it, or maybe the track exit is a little more slippery if you get right to the edge, or maybe the inside curbing is too high for you to use all of it because it upsets the car, or maybe your car understeers too much at corner entry, etc. Things get even more complicated if one corner immediately leads to another corner and you have to determine which one to prioritize. But let’s start with one corner. In this case I’m focusing on Turn 15 at COTA which is a fairly slow 180-degree corner. I circled Turn 15 in Exhibit 1.
Exhibit 1
I’m presenting data from a driver who was just learning the track so there was lots of experimentation with lines happening. And it is important to experiment with different lines because every time that you do that you gather more data to analyze which will help you figure out the best way for you to take the corner. Exhibit 2 shows two different lines taken by this driver and the direction that the driver is heading is counterclockwise.
Exhibit 2
As you can see, the red trace is a wider radius than the yellow trace so is that faster because there is less turning? The answer is no, the segment time for the yellow trace is 6.94 seconds and the segment time for the red trace is 7.367 seconds so the red trace segment time is .427 seconds slower than the yellow trace segment time. These same traces shown in red in Exhibit 3 show the segment that we are analyzing.
Exhibit 3
There are several things to look at here but let’s start with the videos. Exhibit 4 shows three different screen shots of the videos side by side from Corner Entry to Corner Exit.
Corner Entry
Mid Corner
Corner Exit
Exhibit 4
In the Corner Exit screen shots, the cursor is placed where there is the biggest gap between the GPS traces shown in Exhibits 2 and 3. Can you see much of a difference in the driving lines? I’m seeing that the red trace is maybe a few feet wider in the Corner Exit screen shots which aligns with what the GPS traces are showing but otherwise it is very difficult to tell the difference. Video is obviously extremely important but it is even more powerful when combined with data as we are seeing here.
Another bit of information that I like to look at is the Inverse Corner Radius as the color channel on the GPS traces. You can see this in Exhibit 5.
Exhibit 5
Remember, the red trace is the outside trace and yellow (the faster trace) is the inside trace. The areas are red in Exhibit 5 are showing where the car is at it’s tightest radius. Many times this is the point where the driver is apexing the corner but in this case I think this is true for the yellow (inside) trace but I don’t think this is true for the red (outside) trace. Nevertheless, this does show that the car is at it’s tightest turning radius earlier with the red trace than with the yellow trace and this is definitely something to consider when trying to decide which driving line to use.
Let’s look at some of the traditional traces now. Exhibit 6 shows speed, steering, throttle, brake, and I also included longitudinal G’s that are reversed in order to mimic the brake trace.
Exhibit 6
It is always good to look at speed first. Here you can see that I placed the cursor at the minimum speed point and you can see that the minimum speed is about the same. The driver was initially a little faster going into the corner on the yellow trace lap but on the red trace lap the driver releases the brake and the car gains speed. The driver recognizes that this is probably too fast and re-applies the brake. This could have upset the car a little bit or put the driver on a trajectory that they didn’t really want to go in. Nevertheless, it is easy to see that the yellow trace was faster exiting the corner and, in my opinion, the exit speed is almost always more important than entry speed. That extra speed achieved on the yellow trace was due to the fact that the driver was able to get to full throttle sooner. Another interesting aspect shown in Exhibit 6 is that even though there are some significant differences between the brake traces, the longitudinal G’s don’t look so different. But it is clear to see that the control of the weight transfer as the driver was releasing the brake pedal was better on the yellow trace lap. This really matters because in order to find the correct line, you also need to drive the car the way it wants to be driven. It is important to not deviate from that too much because if you aren’t driving the car the same way each time you enter the corner then it is going to be difficult to determine if you need to change how you are driving the car as opposed to the line that you are driving.
There is another thing that I frequently like to look at and that is whether or not the driver is lifting exiting the corner because this is a good indication of the driver’s comfort level. The red trace in Exhibit 7 shows that the driver had a couple of significant lifts exiting the corner on that lap.
Exhibit 7
There are a number of other things that can be looked at as well such as vertical acceleration to see if you are using too much curbing or corner radius to see the exact point that the car is turning or straightening or even if there is an extra turn at the exit if you used too much track. But I think lifting is one of the biggest indicators as to whether or not you are driving the car correctly or if you are comfortable enough in the car to carry the speed that you need to carry to be fast. If you are lifting due to having to quickly the catch the back end then that isn’t necessarily a bad thing but you need to figure out if that lift was enough to slow you down and whether or not you need more patience with throttle application.
If you have a data system in your car then you most likely have a dash that can display predictive lap timing. Looking at +/- your best lap time as you exit the corner is a great way to get immediate feedback as to whether or not what you just did was better or worse than what you did on your best lap. This, combined with experimenting with different lines, is probably the quickest way to figure out if the line that you are driving is at least in the ballpark. But it is also a good idea to watch other cars going through the corners even if they aren’t the same kind of car that you are driving. It is usually pretty easy to tell which cars are the fastest through the corners so pay attention to what they are doing. They may be doing something that you never even thought was possible!
Good luck in your races!